WREC Plant Pathology Updates
Pea Enation Mosaic Virus Detected in Divide County (06/16/16)
Pea Enation Mosaic Virus Detected in Divide County
Be on the lookout for Pea 
Enation Mosaic virus (PEMV). A pea plant exhibiting interveinal chlorosis was found by a crop scout in a field in southern Divide County (Fig 1). Genetic based lab testing by the MSU Regional Pulse Crop Diagnostic Laboratory found that the plant was infected with PEMV. PEMV is a viral disease that can infect many legumes including pea, chickpea, faba bean and lentil and is transmitted by pea aphid and green peach aphid, in addition to several other aphid species. Symptoms can vary based on host and environment, but infected plants will typically develop yellow or translucent flecks on the leaf (Fig 2A), vein clearing and later on “enations” or leaf blisters may appear (Fig 2B). Leaves might also be twisted or edges may have a downward roll. These early symptoms can easily be confused with herbicide damage, nutrient deficiency or other viruses, so laboratory diagnoses is important. PEMV may also cause stunting and a reduction in internode length. Pods may be twisted, deformed or develop a “warty” appearance (Fig 2C). If the plant is infected prior to bloom, pods may not fill normally and yield may be impacted.
Few management options exist for PEMV. Reducing aphid populations with an insecticide application may reduce the secondary spread of the virus. However, it is unclear if that application would be cost-effective. In planning for next year resistance could be an option. Hampton, a PEMV resistant green field pea variety was released, and although it was developed for conditions in the Pacific Northwest, it may be a good option for growers who have problems with this disease.
Plant Pathologist, NDSU Williston Research Extension Center
Pea Seed-borne Mosaic Virus Detected in One Seed Lot from Mountrail County (05/19/16)
Pea Seed-borne Mosaic Virus (PSbMV) is a
viral disease that can cause substantial yield and quality losses in lentils and peas and can also infect chickpeas, faba beans and vetches. Plant symptoms include stunting, pod and leaf deformation, and delayed maturation (Fig 1. top). Seeds may be smaller, and discolored with split seed coats (Fig. 1 bottom). As the name implies the virus can infect the seed and when this seed is planted the virus can spread into the plant. The transmission rate from seed to plant is on average 30% in peas and 44% in lentils. Aphid feeding transmits the virus from infected plants to new hosts during the growing season. Therefore, planting infected seed and high aphid populations put you at the greatest risk for PSbMV.
As part of a NW ND pulse scouting project funded by the Northern Pulse Growers Association, Taheni Jbir (Crop Scout, NDSU WREC) and Dr. Audrey Kalil (Plant Pathologist, NDSU WREC) collected pea and lentil samples from growers in Williams, Divide, Mountrail, McKenzie and Burke Counties.
A total of 10 lentil and 18 pea samples
were collected and analyzed by the NDSU Plant Diagnostic Lab for PSbMV (Fig 2). Low levels of PSbMV were detected in a single pea seed lot from Mountrail County, all other lots were negative for the virus. These results, from a limited number of seed lots, suggest that overall levels of PSbMV in planted seed may be low in NW ND; however, it remains important to scout for aphids weekly up through pod development as this virus can be transmitted very rapidly under high aphid pressure.
Remember that PSbMV infected seed should not be saved and as infected seed may be symptomless, it is recommended to get seed tested for this disease. To submit your seed for testing contact the NDSU Plant Diagnostic Lab https://www.ag.ndsu.edu/pdl
For more information on PSbMV and management options see the NDSU publication Pea Seed-borne Mosaic Virus (PSbMV) in Field Peas and Lentils (PP1704).
2015 Wheat Midge Survey Results
The results of the 2015 survey for Wheat Midge Larvae have been reported. Samples were collected in harvested wheat fields in the fall of 2015 and results predict wheat midge populations for the 2016 growing season. According to Dr. Janet Knodel, NDSU Extension Entomologist, "No soil samples were found with economic population densities of wheat midge (greater than 500 midge larvae per square meter) this past year." The majority of the samples, in fact, did not contain any wheat midge cocoons. This is good news for wheat growers and should reduce insecticide costs in the 2016 season.
For more information about the results of this survey see the article below:
